A few weeks ago, I logged in to Facebook and went to open a chat with a friend, when suddenly the chat window disappeared and was replaced with a little warning symbol and the message "Facebook Chat is experiencing technical problems". Oddly, this was only happening in Safari – I could use chat perfectly fine in Chrome.

A screenshot of the issue.

This went on for a while, until a couple of days after I installed Lion on my MacBook. I was testing out resizing a window whilst holding the Option key (this resizes the window equally from each side as you drag) on a Safari window. I happened to have a Facebook window open as I did it, and once the window got to a certain width, the chat sidebar appeared! I tested a few times, making the window smaller and bigger, and it was definitely the window width determining whether chat was working.

So if you ever run into this issue with Safari and Facebook, try making the window wider. It would be nice if the error message said the window was too small, but at least this seems to work for this particular issue.